Process of refining mineral white oils



Patented Nov. 23, 1943 PROCESS OF REFINING MINERAL WHITE OILS Albert P. Giraltis, Cranford, N. L, assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application October 5, 1940, Serial No. 359.93:

9 Claims.

This invention relates to a process for preparing mineral white oils of a high degree of physical and chemical stability, especially as regards color and chemical inertness to highly polished copper.

White oils are usually prepared from petroleum stocks of about lubricating oil consistency derived from the less parafiinic crudes obtained either as distillates or as residuals. These oils undergo intensive refining toremove substantially all the unsaturated and color forming bodies contained in the crude stocks. The refining is usually effected by treating the oil with sulfuric acid -of concentrations between 93% strength and 20% fuming, preferably in a series of additions with the separation of the sludges formed after each reaction, then neutralizing, and treating the oil to remove sulfonic compounds and finishing either by air blowing or clay treatment. The lower strengths of acid may be employed in the initial stages, and the higher strengths of acid employed in the final treating stages. Treating temperatures up to about 180 F. may beemployed, the highertemperatures being used only withthe lower strenflths of acid. The acid may be replaced in'whole or in part by aluminum chloride or other known intensive refining agents. It has been found advisable with most stocks, however, to give a final treatment with fuming sulfuric acid.- Distillate stocks usually give higher yields of finished oils with slightly lower amounts of reagents than in the case of residual stocks.

The products of such refining consist largely of parailln and naphthene hydrocarbons and have colors between 16+ and Saybolt.

These highly refined oils are often chemically and physically unstable as a result, presumably, of the removal of certain natural inhibitors considered to be present initially in-the oil and believed not to be removed in less intensive refining treatment. This instability gives rise to the development in oils of compounds of poor color and of objectionable taste and odor and also or compounds. corrosive to highly polished copper. These are serious defects in white oils,

' 7 especially in medicinal white oils, which are rebecause it is expensive and somewhat uncertainv in its efiect, and furthermore is not a means'of remedying a defect apparently in the oil itself due to previous refining treatment. The addition to the oil of compounds similar to those supposedly removed in the intensive refining treatment has the disadvantage in most cases of causing ill effects upon other properties of the oil and the disadvantage also of requiring to be handled separately and blended in the oil in certain limited amounts to achieve the best results.

In the preliminary processing of a suitable stock in this invention, the oil is intensively treated, preferably with a mineral acid such as sulfuric acid, to remove unsaturated and chromogenic compounds as in the prior art. To the thus treated oil about an equal volume of alcohol is usually added, and then 10% aqueous sodium carbonate solution to neutralize the oil. Then the alkaline solution is separated and the oil washed with 50% aqueous alcohol to remove traces of sulfonic soaps, and the alcohol and moisture are removed from the oil by blowing first with steam and then with air. A further refining treatment, the main feature of the pres- -ent invention, is then given to the oil to effect chemical and physical stabilization. This special processing of the oils obviates the formation of compounds corrosive to highly polished copper,

and treatment at about C. with 0.01% to 0.1% of a caustic alkali preferably dissolved in the minimum quantity of a relatively volatile solvent preferably either isopropyl or ethyl alcohol to effect solution or dispersion of the alkali, and then percolating through clay. By the term anhydrous amphoteric metal halide active in Fridel-Crafts reactions as used here and in the claims, is designated the halide of a polyvalent amphoteric metal, such as, aluminum chloride, ferric chloride, chromic chloride, zinc chloride and stannic chloride which hydrolyze in the presence of water. The caustic alkali is dissolved or dispersed in the solvent merely as a means of adding the caustic alkali to the oil in an anhydrous and finely divided state and during the treatment of the oil with the alkali at 120 0., this quantity of the solvent is usually removed.

at a temperature oi about 70' C. for about 30 minutes, removing the sludge and filtering, then. adding caustic potash prei'erably dissolved. in the minimum quantity of dry lsopropyl alcohol to efiect solution and in an amount to give the treating efiect oi two pounds or caustic potash per thousand gallons of oil, then air blowing icr about 20 minutes at a temperature between 100 C. and 135 C., then filtering and percolating through clay.

It is appreciated that the halides, especially the chlorides. oi such amphoteric metals as aluminum. zinc, iron and'chrornium. and the caustic alkalis have been previously employed in treating petroleum oils. but it is believed that the treatment according to the present invention is the first to employ a two step super refining process, involving the use oi both an anhydrous higher halide of an amphoteric metal and anhydrous caustic potash as a means of improving the stability of white oil products. Aluminum chloride and the other such anhydrous halides oi the amphoteric metals have been used as general treating reagents, and also in the polymerization and cracking of hydrocarbons. The action oi these halides is extremely complex, depending greatly on'the temperature, the type 01. hydrocarbon, and the impurities. Aluminum chloride. for instance, at atmospheric temperatures reacts with sulfur and nitrogen compounds present as impurities in crude distillates and in the conversion of unsaturated hydrocarbons to less chemically reactive compounds mainly of a saturated and polymerized nature. When the higher distillates are treated with aluminum chloride. a molecular breakdown or cracking occurs. Aluminum chloride used as a treating reagent upon crude distillates and residuals is about the equivalent of treating such stocks with concentrated sulfuric acid.

In the present invention the amphoteric metal halides such as aluminum chloride are used for treating oils which have been previously intensively refined to remove substantially all the chemically reactive unsaturated and chromogenic compounds. The amounts of the reagents employed in the process of the present invention are considerably smaller than those which have been hitherto used tor treating purposes. The use or the anhydrous amphoteric metal halides oi! this invention is moreover merely one step in a-com-* bination treating process. The removal 01' the sludge formed by the halide does not eliminate from .the oil the corrosive compounds. These compounds are apparently finely dispersed in combination with the halide material throughout the oil and it is 'only by treating with anhydrous caustic alkalies that the corrosive compounds are removed.

In the prior art, aqueous caustic alkalies have 7 been employed largely in neutralizing and doctor sweetening processes. Anhydrous caustic alkalies have also been previously employed as treating reagents for petroleum oils and in thecase oi U. 8. Patent No. 2,110,283, to remove corrosive compounds from white 011 stocks. The process of in that the present process is more generally ap- One method or effecting the invention is to pllcable and thatby the use oiihe anhysddtcthedryneutral.normellyrefinedoii'aboutdrou amphoteriemetal 7 mm 0.5% of aluminum chloride. added pref r ly ties of the caustic alkslies an be employed to in the form oiapastemede with sma l quanecnievetnesametrestingefiectonsimilsrstccks. ti yoi o e ms lns h m llre s Asaresultcitheuseoilower amountsoinustie alkalies better colors are obtained on the neutral oils which are reflected in improved in the clay filtering operations by which the are usually finished and also base formation the finished products is practically Indeed. the combination of the treating effects of the anhydrous amphoteric metal halide and the anhydrous caustic alkali efiected by the process of this invention overcomes the instability of been found to be a superior treating process for the preparation or white oil products 01 a high order of chemical and physical stability.

In the preparation of such highly refined petroleum products as the white oils, an important controlling test is that 01' determining under specific conditions corrosion to highly polished copper. In. the usual test in this regard a copper strip is mechanically polished with an inert abrasive material such as Tripoli powder on a dampened reclaimed towel or other cloth material free from sizing. The strip is freed of the abrasive material by dusting with a clean dry cloth and then wiping with filter paper. The size of the copper strip which is employed is convenient for placing in a tour ounce sample bottle, that is, strips measuring inch by 3 inches. The polished strip is then placed in a clean dry tour ounce bottle containing suificient oil to immerse completely the strip. The bottle is stoppered with a clean stopper and placed in a constant temperature bath at a temperature of 210 1 for two hours. At the end oi! the twohour period, the sample is removed from the bath and the appearance of the copper strip compared with the appearance of a similarly polished 00pper strip which has been heated in an adjacent four ounce bottle containing air. The presence oi! corrosive copper substances in the oil sample is indicatedby the .difierence in discoloration between the copper strip immersed in' the oil sample and on the blank copper strip. Th results are reported as:

I Sunlighfiaste and odorrest' 50cc. of oil in clean four ounce'bottle. stoppered with clean cork' stopp r is exposed to natural sunlight. At certain intervals of time (5, 10, 15. and'60 min), the sample is'tested-to determine asaaooo An oil of lubricating consistency having a viscosity of 90-100 seconds Saybolt at 100 F. derived from a Mid-Continent crude was treated with 44% of its volume of 20% fuming sulfuric acid, the sludge separated, and the oil phase neutralized with a 10% aqueous solution of sodium carbonate, then washed several time with 50% aqueous isopropyl alcohol solution to remove the oil soluble sulfonates, and then blown with steam and then with air to remove traces of alcohol and moisture present. The resultant oil had a Saybolt color of 19+, a No. copper test value,

and an ash value of less than 0.01%. Five samples of this oil were taken and treated as follows:

1. Aluminum chloride in the amount of 0.5% (wt./volume-basis) in the form of a paste was made with a small quantity of the oil and added to the bulk of the oil. The aluminum chloride was kept suspended in the oil during the treatment for 30 minutes, at 75 C., by active ag tation. The gelatinous sludge remaining in the oil after treatment was removed by contacting with filter aid and then passing through a Buchner funnel. The oil was then steamed for minutes at 110 C. to remove hydrogen chloride and odors which had developed during the treatment with aluminum chloride, then dried by filtering through absorbent paper. The oil was then treated, at 120 C., for 20 minutes with 0.025% (wt./volume) of caustic potash dissolved in the minimum quantity of isopropyl alcohol. The alcoholic solution was then separated and the oil was air blown at 120 C. for 20 minutes to remove all traces of alcohol. The oil at this stage I had a Saybolt color .Of 21+. The oil was then percolated through Attapulgus clay (30-60 mesh) at room temperature. The resultant oil was tasteless, odorless, had a Pass No. 1 copper test value, and had a color of +30 Saybolt. The oil did not develop any sulfurous odors when exposed to natural sunlight for a period of 60 minutes. The oil had a Saybolt viscosity at 100 F. of 86 seconds, and at 212 F. of 38 seconds.

11. The second sample of the oil was treated similarly to the first sample except that the 0.025% (wt/volume) caustic potash was dissolved in the minimum amount oi. water to effect solution. The thus treated oil failed to pass the copper corrosion test.

III. Th third sample of the oil was treated with 0. of anhydrous aluminum chloride (wt./volume basis) added in the form of a paste made with a small quantity of untreated oil, then incorporated in the body of the oil, and maintained suspended in the oil by agitation for .30 minutes. The gelatinous sludge was separated by contacting the filter aid and filtering through a Buchner funnel. The oil was steamed for 10 minutes at 110 C. to remove hydrogen chloride and other mal odors which had developed in the oil during treatment with aluminum chloride.

The resultant oil had a Saybolt color of 26+, and

after percolation through Attapulgus clay (30-60 mesh) gave a No. 5 copper test.

IV. A fourth sample of theoil was treated at 120 C. for 20 minutes with 0.025% (wt/volume) of caustic potash dissolved in the minimum quantity of isopropyl alcohol to effect its solution. The thus treated oil had a Saybolt color of 10+. After percolation through clay (30-60 mesh) the resultant oil was tasteless, odorless, and had a +30 Sayboit color. The thus treated oil had a No. 4 copper test and developed a garlic odor on exposure to sunlight for 5 minutes.

V. The fifth sample of oil was percolated through Attapulgus clay (30-60 mesh). This oil was tasteless and odorless and had a Saybolt color of 30+. It gave a No. 5 copper test and developed a garlic odor upon exposure to sunlight for 5 minutes. The Saybolt viscosity at 100 F. was 86 seconds, and at 210 F. was 38 seconds.

It is demonstrated by the treating of the five samples of the oil that a combination treatment of aluminum chloride followed by alcoholic potash improves both the color, odor, taste, and chemical stability of the oil as regards inertness to highly polished copper. The oil without such treatment is shown to be definitely unstable in regard to color, odor, taste, and corrosiveness towards highly polished copper. It is only the combination treatment with aluminum chloride, followed by alcoholic potash that is efiective in producing highly stabilized oil. It is also demonstrated that the small amount of aluminum chloride'employed has no effect whatever on the viscosity of the oil.

Example 2 'In a test to demonstrate the effect of the presence in the oil of soluble sulfonates, 0.06% of a purified oil soluble soap was added to a sixth sample of the oil used for subsequent treating in Example 1. The blended oil after percolation through 5% clay gave a No. 2 copper test rating.

The refining action inherent in the process of the invention is not associated therefore with the removal of any sulfonic compounds from the oil.

Example 3 The efiect of treating reagents other than aluminum chloride in small quantities is shown by another series of treatments of the same base normally refined oil as previously employed.

1. 1% by volume of 20% fuming sulfuric acid was added to the oil and agitated for one hour. The oil was treated with an equal volume of isopropyl alcohol solution containing 0.025% (wt/volume) of caustic potash and filtered through several sheets of absorbent paper. After percolation through Attapulgus clay (30-60 mesh), the oil gave a No. 5 copper test.

II. The oil was treated with an 0.5% anhydrous ferric chloride at '75 C. for 30 minutes. The reagent was added in the form of a paste. The oil was then filtered free of sludge and treated at 120 C. with an equal volume of an isopropyl alcoholic solution containing 2 pounds of caustic potash per thousand gallons of oil to be treated.

' The alcoholic solution was separated and the oil upon exposure to natural sunlight for 60 minutes.

The treatment according to the, invention iniproves the stability of white oil products in at least four respects: namely, color. odor, taste, and

development of corrosiveness towards highly pol-.

ished copper. As a result of processing oils according to the invention, it is noted also that the yields in the clay filteringoperations by which the oils are usually finished are improved. This treating eifect upon normally refined oils of lu-' bricating oil consistency is common to all the higher valent halides of the amphoteric metals which hydrolyze in the presence of water in combination with caustic alkalis dissolved or finely dispersed inan organicsolvent which readily vaporizes from the treated oil. The halides of the trivalent elements however, particularly alumianhydrous metal chloride isthat of a trivalent element.

the unstable and color-forming bodies, separatnum chloride and ferric chloride have been found to be preferable in combination with potassium hydroxide dissolved in either isopropyl or ethyl alcohol. In additon to the improvement of white oil products of lubricating oil consistency, highly refined oils in the naphtha'and kerosene boiling ranges can also be advantageously treated by the method pf the present invention. The products obtained in such cases are suitable for the preparation of solvents, lacquers, spray compositions and in the preparation of similar type materials.

While the invention has been described in detail, and a number of illustrated examples have been given, it is to be'understood that the invention is not limited thereby .but same have been given for the purpose of conveying an appreciation of the scope and nature ot the invention. It will be obvious to those skilled in the art that variations of the process can be made within the spiritof theinvention. 1

Whatisclaimedis:

1. The process of refining mineral white oils which comprises, treating a petroleum oil with sulfuric acid of above 93% concentration to 'remove substantially all the unsaturated and coloring the sludge after each addition, then neutralizing the, oil withan aqueous alkaline solution, separating the aqueous solution, treating the oil with an about 50-50 water isopropyl alcohol mixture to remove sulfonate soaps, treating the oil with steam and then with air to remove traces ofisopropyl alcohol and water, then treating the oil with an anhydrous metallic chloride selected from the group consisting of aluminum chloride, ferric chloride, chromic chloride, zinc chloride and stannic chloride in an amount between about .5% to 1% by weight of the oil, separating the sludge so formed, treating the resultant oil withan anhydrous alcoholic solution of 0.01% and 0.1% of a caustic alkali and then treating with clay. 6. Process according to claim 5 in which the anhydrous metallic chloride is aluminum chloride.

'1. Process according to claim 5 in which the caustic alkali employed is caustic potash.

8. Process according to claiiri 5 in which the anhydrous metallic chloride is aluminum chloride and the caustic alkali employed is caustic potash.

9. Process of refining mineralwhite oils which comprises treating a petroleum oil of lubricating forming bodies, separating thesludge, ,neutralizing the oil with an'alkaline solution,:separating the alkaline solution, treating the oil with about queous alcohol to remove sulfonate soaps, treating the resultant product with from about .5% to 1% of an anhydrous metallicchloride selected from the group consisting ofaluminum chloride, ferric chloride, chromic chloride, zinc chloride and stannic chloride, separating the sludge so formed'and then treating the oil with from'about .01% 'to 1% of an anhydrouscaustic alkali 2. according to claim l in which the oilconsistency with 20% fuming sulfuric acid in a series of additions to remove substantially all the unsaturated and color forming bodies, sepmating the sludge after each addition, then neutralizing the oil with-a10% aqueous solution of sodium carbonate, separating the aqueous solution, washing the oil several times with a 50% aqueous isopropyl alcohol solution to' remove oil soluble sulfonates, treating the oil with steam and then with air to remove traces ofisopropyl alcohol and water, then treating the oil with 0.5% of aluminum chloride for 30 minutes at C., separating the sludge so formed, treating the resultant oil at C. with 0.025% of caustic potash dissolved in a minimum quantity of isopropyl alcohol, blowing the oil atl20 (J. to remove the alcohol and then percolatingthrough clay.

v ALBERT P. GIRAITIS. 

